A base station network in a mobile communication system comprises primarily base stations (BS) and a base station controller (BSC). The base station controller controls the operation of the base stations. The BSC is connected to a mobile switching center (MSC). The base stations provide connections to mobile phones through the air interface. The base stations are connected to the BSC through a radio link, copper cable or optical cable. Between the base stations and base station controllers there are usually cross-connects which take care of the switching of connections between the various devices. The tasks of the BSC include controlling the transmission power of mobile stations and carrying out handovers for mobile stations. The base station controllers are connected to a mobile switching center which handles the mobile telephone traffic in its geographical area. Its tasks include routing of calls, call management and termination of calls. Furthermore, the mobile switching center is connected to registers containing user information such as e.g. the home location register HLR and visitor location register VLR and a network management system NMS. FIG. 1 shows a block diagram of a typical base station network architecture. The base station network comprises base stations 10 and base station controllers 20. The base station controller 20 is connected to a mobile switching center MSC 30 in the mobile communication network. In addition, FIG. 1 shows mobile stations 5 connected to the base station network.
As the Internet gains more popularity, the technology involved, in particular the technology associated with IP (Internet Protocol) networks, has become cheaper and has been introduced in many fields of application. IP network technology is already being used in mobile communication systems as well, especially in setting up base station networks. In an IP network each device in the network has a unique address within the network. If a device has got several interfacing ports to the network, each port is given an IP address of its own. There are two versions of the IP protocol. Version 4 of the IP protocol (IPv4) is specified in the document RFC 791. Version 6 of the IP protocol (IPv6) is specified in the document RFC 1883.
An IPv4 address consists of a string of 32 bits. FIG. 2 illustrates the structure of IPv4 address. IPv4 addresses are currently divided into five classes: A, B, C, D and E. The most significant bits in the address indicate the class of the address. A, B and C class IP addresses are divided into two parts: the net part and the host part. The net part identifies the network to which the host is connected, and the host part identifies the host's connection port to the network. By reserving more bits to the net part and fewer bits to the host part it is possible to assign addresses to an overall network architecture comprising a large number of discrete networks. Such a case of course involves the restriction that a discrete network cannot contain very many recipients. Conversely, if we have a few large networks with a large number of users in them, then it is best to choose a net part comprising fewer bits and a host part comprising many bits. A D-class address comprises a so-called multicast address, and class E is reserved for future use. IP addresses are unique, so granting and assigning IP addresses must be supervised so that one and the same address not be given more than once.
A new device attached to an IP network needs an IP address of its own. A popular way to implement the allocation of an IP address to a new device attached to the network is to have the new device request the IP address from a DHCP (Dynamic Host Configuration Protocol) server or BOOTP (Bootstrap Protocol) server either in the same or in a different network. The DHCP server keeps track, in a centralized manner, of the IP addresses required by a network in the geographical area assigned to it. The DHCP or BOOTP server allocates the new device a free IP address and sends information about it to the new device. As soon as the new device has got an IP address, it is able to communicate in the network. Another alternative, somewhat more complicated though, is to program an IP address for the new device already before it is delivered to its final destination, but this calls for very careful network planning and maintenance.
If the network topology is such that a router is connected to an outside network via one route only and to the internal network hierarchy via multiple ports, then the network elements connected to each one of the ports can be regarded as discrete subnetworks. Therefore, a so-called subnetwork mask can be used in the IP addresses. Subnetwork mask means that the host part of the IP address is divided into two parts: a part specifying the subnetwork and the host part proper. Thus, when the subnetwork is being implemented, the IP addresses in the subnetwork can be compiled such that the combination of the part specifying the subnetwork and the net part proper is considered the internal net part of the subnetwork.
In order to make network planning easier, the base station network can be divided into subnetworks which are planned separately. A subnetwork may consist of e.g. several base stations located in one and the same geographical area. In addition, a so called DCN (Data Communication Network) for the subnetwork has to be set up for the purpose of network control. Subnetwork planning is usually quite a laborious and time-consuming phase in network planning.
If human errors such as incorrectly installed cross-connections, incorrectly positioned radio links etc. occurred during the installation of a network, a connection to a DHCP or BOOTP server cannot be established. Such errors in the installation stage of the network are quite usual due to e.g. differing installation schedules of the various parts of network. A new device must also be provided with a connection to the network control system, whereby this, too, is made uncertain by the factors mentioned above. Therefore, an easier base station installation method is needed